
// 注意这里的代码是在顶层作用域中存在的
let K = {
    single: function( selector ){
        return document.querySelector( selector );
    },
    all: function( selector ){
        return Array.from(document.querySelectorALL( selector ));
    },
    on: function( target , type , listener , capture = false ){
        target.addEventListener( type , listener , capture );
    }
}